MongoDB was rejecting status updates to 'tts_failed' and 'render_failed'
because these values weren't in the schema validator's enum, even though
they were defined in the Python JobStatus model.
This caused TTS failures to leave jobs stuck in 'tts_generating' status
with no error feedback to users - the WriteError from MongoDB prevented
the status and error fields from being updated.
The migration adds both failed statuses to the jobs collection validator.
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
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